The present disclosure relates to measurement of flow of a process fluid in an industrial process. More specifically, the present disclosure relates to measuring a flow rate with an averaging pitot tube and thermal mass sensor.
Flare gas flow measurement is important for a number of reasons including mass balance, energy conservation, emissions monitoring, and regulatory considerations. For example, natural gas is commonly associated with petroleum deposits. Gas may be released from petroleum deposits during petroleum extraction. Systems which are used to release natural gas generally operate at relatively low flow rates (purge flow conditions), but also may experience unpredictable conditions with relatively high flow rates (upset conditions). An averaging pitot tube primary element (APT) (such as the Annubar® APT available from Emerson Process Management which is suitable for measuring flow rates in upset conditions may be unable to generate a measurable differential pressure (DP) signal during purge flow conditions. Thermal mass flow sensors may be used to measure flow rates in purge flow conditions are unable to generate accurate flow rate readings during upset conditions. Measurement of flow rates may be made using ultrasonic instruments, but such instruments are typically expensive.
Natural gas is often burned at its extraction site to mitigate environmental impact and to promote worker safety. An estimated 150 billion cubic meters of gas are burned annually in flare systems. Oil and gas operators are required to monitor and report the amount of gas flared annually. To accurately report the amount of gas flared, flare metering applications typically target an uncertainty of +/−5% of mass flow rate of the gas that is flared.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.